Cellular communication systems and reuse of radio frequency channels within such systems are known. Channel reuse is important because of the limited number of channels available and because of the large number of users. Reuse of communication channels within a cellular system is limited to areas where sufficient distance exists among reusing radios such that interference is maintained below an acceptable level.
Frenkiel (U.S. Pat. No. 4,144,411) provides one method of reusing communication channels among a number of cell sites. Under Frenkiel, narrow-beam antennas allow seven cells per subarray before use of a channel is repeated in a cellular system. The seven cell subarray is repeated across a communication system.
Under Frenkiel three 120-degree directional antennas are located at a center of a cell. The three 120-degree directional antennas divide the cell into three sectors. In accordance with the Frenkiel invention, each of the sectors are allocated one or more communications channels and a given number of cells are used to form a subarray for providing communication access through a predetermined number of communication channels. The communication channel allocations are repeated from subarray to subarray.
While the method provided by Frenkiel works well over a flat, homogeneous, idealized terrain, difficulties are often experienced in more hostile terrain, where barriers interrupt the orderly repetition of subarrays based upon some regularly presumed (co-channel) interference level. To accommodate barriers such as hills or tall buildings, a base site of a cell is often moved to a more convenient location, such as to the top of a building or hill. The use of a more convenient location often increases interference and disrupts the reuse pattern resulting in less efficient use of communication resources. Where a base site is located at the top of a hill, the elevation may result in mutual interference between the base site on the hill and base sites located around the hill.
Mutual interference within a communication system is closely related to the topology of the terrain in which the system is to be used. The efficient use of communication channels, on the other hand, is closely related to reusing channels as close together, geographically, as possible. Where because of terrain, or otherwise, the orderly layout of base sites is disrupted, then the spacing and assignment of channels becomes more difficult, often requiting a trial-and-error approach. Because of the importance of communication systems a need exists for a more convenient method of displaying attributes of a communication system in a manner that relates such information to a geographic context.